From 1c1ba5b4bd45c1fe42e98d39b5ac7c743d78dd44 Mon Sep 17 00:00:00 2001
From: Yang Shi <yang.shi@linux.alibaba.com>
Date: Wed, 1 Apr 2020 21:06:23 -0700
Subject: [PATCH] mm: swap: use smp_mb__after_atomic() to order LRU bit set
References: git fixes (mm/vmscan)
Patch-mainline: v5.7-rc1
Git-commit: 9a9b6cce630d14851ab09534b6462258486048cd
Memory barrier is needed after setting LRU bit, but smp_mb() is too
strong. Some architectures, i.e. x86, imply memory barrier with atomic
operations, so replacing it with smp_mb__after_atomic() sounds better,
which is nop on strong ordered machines, and full memory barriers on
others. With this change the vm-scalability cases would perform better on
x86, I saw total 6% improvement with this patch and previous inline fix.
The test data (lru-file-readtwice throughput) against v5.6-rc4:
mainline w/ inline fix w/ both (adding this)
150MB 154MB 159MB
Fixes: 9c4e6b1a7027 ("mm, mlock, vmscan: no more skipping pagevecs")
Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Tested-by: Shakeel Butt <shakeelb@google.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Link: http://lkml.kernel.org/r/1584500541-46817-2-git-send-email-yang.shi@linux.alibaba.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Mel Gorman <mgorman@suse.de>
---
mm/swap.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/mm/swap.c b/mm/swap.c
index 9ad9ad8ef17d..3a4be04bdb96 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -887,7 +887,6 @@ static void __pagevec_lru_add_fn(struct page *page, struct lruvec *lruvec,
VM_BUG_ON_PAGE(PageLRU(page), page);
- SetPageLRU(page);
/*
* Page becomes evictable in two ways:
* 1) Within LRU lock [munlock_vma_page() and __munlock_pagevec()].
@@ -914,7 +913,8 @@ static void __pagevec_lru_add_fn(struct page *page, struct lruvec *lruvec,
* looking at the same page) and the evictable page will be stranded
* in an unevictable LRU.
*/
- smp_mb();
+ SetPageLRU(page);
+ smp_mb__after_atomic();
if (page_evictable(page)) {
lru = page_lru(page);